The present invention generally relates to picture generating apparatuses for rotary recording medium reproducing apparatuses, and more particularly to a picture generating apparatus for a rotary recording apparatus which controls the rotational speed of a rotary recording medium (hereinafter simply referred to as a disc) which is being played, so that a horizontal scanning frequency of a video signal which is recorded on the disc is reproduced at a horizontal scanning frequency of a predetermined system which is determined by a monitoring apparatus which displays a reproduced picture. The picture generating apparatus according to the present invention generates a picture related to an address information which indicates the position of a recorded track on the disc, for example, and displays the generated picture in a part of the reproduced picture which is displayed on the monitoring apparatus.
A video disc which is recorded with a color video signal as variations in geometrical configuration, is known. In such a video disc, the color video signal is converted into a predetermined signal format together with an audio signal, before being recorded as the variations in the geometrical configuration. The color video signal is converted into the predetermined signal format which is different from a standard television system, before being recorded on the video disc. However, the field frequency and the horizontal scanning frequency (in other words, the number of scanning lines), are the same as the field frequency and the horizontal scanning frequency of the standard television system. Since there are two popular television systems which are presently being employed in most parts of the world, one being a first system having a field frequency of 60 Hz (59.94 Hz in the case of a color video signal) and 525 scanning lines and the other being a second system having a field frequency of 50 Hz and 625 scanning lines, it is necessary to prepare at least two systems for recording the video disc.
A reproducing apparatus was proposed in a U.S. Pat. No. 4,445,143 of which the assignee is the same as the assignee of the present application. According to this proposed reproducing apparatus, the video disc is played while the rotational speed of the video disc is controlled so that a horizontal synchronizing signal of the recorded video signal is reproduced with a predetermined frequency which is in conformance with a television system with which the reproduction is to be carried out. Thus, video discs which are recorded with color video signals of different television systems, may be played compatibly according to this proposed reproducing apparatus.
As is well known, the color television system is not unified throughout the world. There are two main differences among the different color television systems, the first main difference being the number of scanning lines and the field frequency, and the second main difference being the transmission format of the chrominance signal. The color television systems are divided into three types, that is, the NTSC system, the PAL system, and the SECAM system, according to the transmission format of the chrominance signal. However, the chrominance signal which is transmitted, is made up of two kinds of color difference signals as is well known. Because the video disc reproducing apparatus is intended to only play the video disc and reproduce the recorded color video signal, the chrominance signal which is recorded on the video disc need not have a signal format which is in conformance with one of the NTSC, PAL, and SECAM systems. In other words, the chrominance signal can be recorded on the video disc with a common signal format which is independent of the color television system with which the reproduction is to be carried out. In this case, the chrominance signal which is reproduced from the video disc can be converted into a signal which has been modulated with a predetermined modulation system which is in conformance with a desired standard television system among the NTSC, PAL, and SECAM systems, when supplying a reproduced color video signal to an external monitoring television receiver as a standard system color video signal from the video disc reproducing apparatus. Accordingly, with respect to the different transmission formats of the chrominance signals, it is possible to achieve compatibility by providing in the video disc reproducing apparatus a converter for obtaining a carrier chrominance signal which is in conformance with a predetermined standard television system.
On the other hand, concerning the first main difference described before, there basically are two systems at the present. The first system employs 525 scanning lines per frame and the field frequency is 60 Hz (59.94 Hz in the case of a color video signal). The second system employs 625 scanning lines per frame and the field frequency is 50 Hz. The difference between the horizontal scanning frequencies in the two systems is therefore only in the order of 0.7%. Further, the difference between the field frequencies in the two systems, is only to a degree that is adjustable in a commonly available television receiver. Thus, in the proposed reproducing apparatus described before, the rotational speed of the video disc was controlled so that the recorded horizontal synchronizing signal is reproduced from the video disc with a horizontal synchronizing signal which is in conformance with a color television system with which the reproduction was to be carried out in the monitoring television receiver. As a result, it was possible to compatibly play the video discs which have been recorded according to different color television systems, and obtain a reproduced picture which was both horizontally and vertically synchronized.
Accordingly, in a case where the color video signal which is recorded on the video disc at a rate of 4 fields per revolution of the video disc and is recorded for 60 minutes on one recording surface of the video disc, employs the first system described above, 54000 tracks are formed on one recording surface of the video disc when the number of tracks formed in one revolution of the video disc is one. Of course, the color video signal which is reproduced from this video disc can be displayed on the monitoring television receiver of the first system, by rotating the video disc at a rotational speed of 899.1 rpm. However, the color video signal which is reproduced from this video disc can also be displayed on the monitoring television receiver of the second system, by rotating the video disc at a rotational speed which is 0.7% slower than 899.1 rpm. In this case, the 60-minute program takes approximately 25 seconds longer to reproduce, however, the reproduced picture which is displayed on the monitoring television receiver of the second system is satisfactory from the practical point of view. Similarly, in a case where the color video signal which is recorded on the video disc employs the second system, 45000 tracks are formed on one recording surface of the video disc. When this color video signal is to be reproduced from the video disc and displayed on the monitoring television receiver of the first system, the video disc is rotated at a rotational speed which is 0.7% faster than the original rotational speed of 750 rpm. In this case, the 60-minute program will take approximately 25 seconds shorter to reproduce, but the reproduced picture which is displayed on the monitoring television receiver of the first system is satisfactory from the practical point of view. Thus, it is possible to satisfactorily display the color video signal of the second system which is reproduced from the video disc, on the monitoring television receiver of the first system.
Generally, various address signals are recorded on the video disc, for the purpose of random access and the like. For example, the address signals indicate the position of a recorded track in terms of a recording time from a lead-in position on the video disc, in terms of a sequence of recorded programs, and in terms of a number of recorded tracks from the lead-in position. The address signals are multiplexed and recorded in a predetermined duration within the vertical blanking period of the video signal. Conventionally, there was a video disc reproducing apparatus having a picture generating apparatus for generating a picture information which is to be displayed in a part of the reproduced picture. For example, the picture generating apparatus generated a picture information related to an address information which was being reproduced in order to constantly let the operator know the position of the pickup reproducing element, generated a picture information related to a target address information during a random access operation. The pickup reproducing element was a scanning stylus, or a detector which projected a light beam on the disc and detected the change in the light intensity of the reflected or transmitted light, for example.
The display of the picture information, which is generated from the picture generating apparatus, in a part of the reproduced picture, is referred to as a "on screen display". The "on screen display" was made in white, for example, at an upper right corner of the reproduced picture or at other corner parts of the reproduced picture so as not to greatly interfere with the original reproduced picture.
However, in the case where the monitoring television receiver made exclusively for the first system is to display the video signal which is reproduced from the disc which has been recorded with the video signal of the second system, by use of the proposed disc reproducing apparatus described before, the "on screen display" in the reproduced picture is made at a position which is higher than the position of the "on screen display" which is made when playing the video disc which has been recorded with the video signal of the first system, due to the different number of horizontal scanning lines employed in the two systems. In other words, the number of scanning lines employed in the second system is 625 which is 100 more than the number of scanning lines employed in the first system. Hence, when the video signal of the second system, in which the horizontal scanning frequency has been converted to 15.734 kHz, is displayed on the commonly available television receiver which is made exclusively for the first system and does not have a means for converting the vertical scanning frequency from 60 Hz to 50 Hz, the reproduced picture becomes stretched in the vertical direction thereof. This is because the display made in this case, may be considered equivalent to adding 50 horizontal scanning lines at both the upper and lower parts of the picture so as to display a picture having 625 scanning lines. On the other hand, in the conventional picture generating apparatus, the position of the "on screen display" was determined by a counted value in a counter which counted the horizontal synchronizing signals immediately after the trailing edge of a vertical synchronizing pulse. For this reason, compared to the case where the first system disc was played, the position of the "on screen display" moved to a position which is higher by 50 scanning lines, that is, by 25 counts in the counter if the interlacing was taken into account, when playing the second system disc and displaying the reproduced picture on the television receiver made exclusively for the first system. Consequently, a portion of or the full "on screen display" could not be made within the reproduced picture.